1. Field of the Invention
The present invention relates to a grinding sludge compacting machine for compressing a grinding sludge of hardened component parts produced in a grinding line, for example, a grinding sludge of ferrous component parts such as inner and outer races and rolling elements and others of rolling bearings and other bearing steel material, to thereby provide a briquette.
2. Description of the Prior Art
Ferrous component parts of rolling bearings such as inner and outer races and rolling elements are, after having been hardened, subjected to a grinding process to grind raceways and others. Powdery grinding scraps produced as a result of the grinding are discharged as a sludge together with a coolant to the outside of the system and are then filtered so that the coolant can be reused. The grinding sludge left as a result of the filtration is in most cases buried in landfill.
However, not only is the use of the grinding sludge for landfill generally considered undesirable from the standpoint of environmental pollution, but also it is obvious that in view of the waste treatment sites reaching an dead end, the grinding sludge would no longer be used for land reclamation. Although the amount of the grinding scraps produced as a result of the grinding is relatively small as compared with the amount of cutting scraps, a mass-production line for manufacture of, for example, bearings results in a relatively large quantity of the grinding scraps
For this reason, it has been suggested to compress the grinding sludge by squeezing to provide a compressed material (referred hereinafter to as a xe2x80x9cbriquettexe2x80x9d) so that the coolant squeezed therefrom can be reused while the briquette can be used as a material for steel production.
While the grinding sludge using an aqueous coolant can easily be compressed to provide the briquette, an oil-based coolant has a higher viscosity than that of the aqueous coolant and, therefore, the grinding sludge using the oil-based coolant poses various problems in compressing it. By way of example, during squeezing the oil-based coolant is difficult to be drained and even though the pressure used during squeezing is increased, compression of the grinding sludge to a required strength cannot be achieved. For this reason, compression of the grinding sludge containing the oil-based coolant has not yet been practiced.
Compression of the grinding sludge is considerably affected by the viscosity of the coolant being squeezed during the compressing process. Not only where the coolant is oil-based, but also where it is water-based, it tends to be considerably affected by the coolant viscosity. In particular, at the time of the start-up in the morning during the winter season, the grinding sludge compacting machine and the grinding sludge are both cold with the coolant consequently exhibiting a high viscosity enough to make it difficult for the coolant to be discharged through a gap. Accordingly, when attempt is made to forcibly apply a pressure to the grinding sludge to compress the latter, the coolant and the grinding scraps are mixed to form a sludge which subsequently flow out, making it difficult for the grinding sludge to be satisfactorily compressed.
As a machine for compressing a grinding sludge containing an oil-based coolant, the applicant(s) of the present invention has suggested a machine in which the pressure used for squeezing is controlled to a predetermined value and a predetermined compressing speed such as described in the Japanese Laid-open Patent Publication No. 2001-315000. According to this prior invention, the grinding sludge containing the oil-based coolant of a high viscosity can be satisfactorily compressed. However, it cannot accommodate change in parameter that affects the squeezing and, in the event that the parameter such as, for example, the ambient temperature or the oil content in the grinding sludge that affects the squeezing changes, it may be suspected that no satisfactory squeezing to provide the briquette can be achieved.
In general, because the grinding sludge contains so large a quantity of the coolant that the grinding sludge cannot be squeezed directly, the grinding sludge containing the coolant is, prior to being squeezed, filtered to provide a concentrated sludge which is subsequently compressed by the grinding sludge compacting machine to provide a briquette.
The grinding sludge compacting machine for compressing the grinding sludge has hitherto been available in the following two types; a gate type and a plug-like double cylinder type.
The gate type grinding sludge compacting machine includes, as shown in FIG. 9, a cylindrical mold 81 for accommodating a grinding sludge therein, a gate 82 for closing one end of the cylindrical mold 81 and a pressure applying piston 83 reciprocatingly movably inserted in the cylindrical mold 81 from the opposite end thereof. By pressing the piston 83 by means of a pressure applying cylinder 85, the grinding sludge can be squeezed within the cylindrical mold 81 to provide a briquette B.
The grinding sludge compacting machine of the plug-like double cylinder type includes, as shown in FIG. 10, a cylindrical mold 91 and first and second pressure applying pistons 92 and 93 reciprocatingly movably inserted in the cylindrical mold 91 through opposite ends thereof, respectively. The first and second pistons 92 and 93 are pressure applying sub-piston and main piston, respectively, which are driven by a sub-cylinder 94 and a main cylinder 95, respectively. The sub-piston 92 is held at a fixed position during the squeezing process and is adapted to be retracted away from the cylindrical mold 91 when the resultant briquette B is to be ejected out of the cylindrical mold 91.
The foregoing two systems have their own problems which will now be discussed.
(1) Gate Type (FIG. 9)
Since the sliding gate 82 is almost unable of being sealed against the cylindrical mold 81, it works while the grinding sludge is intruded into a gap therebetween and, for this reason, frictional wear is apt to occur. Once rattling occurs because of it, the gap increases and, once this gap increases to a size exceeding a limit, either the grinding sludge will blow off during the compressing operation, or the sludge will solidify within the gap between the gate 82 and the end face of the sleeve 81 with the coolant being consequently unable to be drained, resulting in difficulty in accomplishing the compression of the grinding sludge. Also, since the gate selectively open or close while the briquette B is purged firmly against the gate 82, frictional wear of respective contact surfaces of the gate 82 and the briquette B, respectively, progresses. Once the quantity of the frictional wear increases to a value in excess of a limit, the phenomenon similar to that discussed above occurs, resulting in difficulty in completing the compression of the grinding sludge.
(2) Plug-Like Double Cylinder Type (FIG. 10)
At the time of compression and ejection of the briquette B, the briquette B is pushed by the pressure applying main cylinder 95 while an outer peripheral surface of the briquette B is firmly urged against an inner peripheral surface of the sleeve 81. For this reason, the inner peripheral surface of the sleeve 91 is susceptible to frictional wear and, when in the last, a gap between an outer peripheral surface of the sub-piston 92 and the inner peripheral surface of the sleeve 91 increases to a size in excess of a limit, either the grinding sludge will blow off during the compressing operation, or the sludge will solidify within the gap between respective outer peripheral surfaces of the pistons 92 and 93 and the inner peripheral surface of the sleeve to such an extent that the coolant cannot be drained satisfactorily, resulting in difficulty in completing the compression of the grinding sludge.
The present invention is, therefore, intended as its primary object to provide a grinding sludge compacting machine capable of satisfactorily compressing a grinding sludge, containing a coolant originating from a grinding line for hardened component parts, even though a parameter that would affect the squeezing process changes.
Another object of the present invention is to provide a capability of satisfactorily achieving a compression regardless of change in temperature.
A further object of the present invention is to provide a capability of efficiently compressing the grinding sludge regardless of change in content of the coolant in the grinding sludge.
A still further object of the present invention is to provide a grinding sludge compacting machine of the type referred to above that is robust to frictional wear, capable of satisfactorily compressing the grinding sludge and capable of being operated stably for a prolonged period of time.
To accomplish these objects, the present invention in accordance with one aspect thereof provides a grinding sludge compacting machine for making a briquette of a grinding sludge by squeezing a concentrated grinding sludge that is a grinding sludge which has been produced in a grinding line by grinding hardened component parts while containing a coolant and which is obtained by filtering the grinding sludge. The grinding sludge compacting machine includes a press unit having a squeezing chamber defined therein and operable to compress the concentrated sludge by application of a pressure within the squeezing chamber, and a press control means for controlling the press unit. The press control means includes a parameter and compressing speed setting means in which a relation between a predetermined parameter that affects the squeezing by the press unit and a compressing speed of the press unit is set, a parameter measuring means for measuring the predetermined parameter, and based on the result of measurement by the parameter measuring means, a compressing speed control means for controlling the compressing speed of the press unit in accordance with a content set by the parameter and compressing speed setting means.
When the grinding sludge is being squeezed to eventually provide a briquette, the compressing speed is affected by the viscosity of the coolant and the fine interstices in the grinding sludge and in turn affects the squeezing process and a result thereof considerably. A proper compressing speed depends on various parameters such as, for example, the viscosity of the coolant. However, according to the first aspect of the present invention discussed above, the relation between the predetermined parameter which would affect the squeezing and the proper compressing speed of the press unit is determined and is then set in the parameter and compressing speed setting means so that during the squeezing operation the predetermined parameter can be measured by the parameter measuring means to enable the compressing speed to be controlled in accordance with the relation between the predetermined parameter and the compressing speed that has been set in the parameter and compressing speed setting means. Accordingly, even though the parameter that affects the squeezing varies in numerous ways, the grinding sludge compacting machine can accommodate such change to compress the grinding sludge satisfactorily and efficiently to provide a satisfactorily finished briquette.
Preferably, the predetermined parameter is the temperature selected from the group consisting of the temperature of the coolant contained in the concentrated sludge, the ambient temperature of the press unit and a temperature of a predetermined portion of the press unit. In this case, the parameter measuring means preferably measures the temperatures or the ambient temperature and, based on a result of measurement performed by the parameter measuring means, the compressing speed by the press unit is controlled by the compressing speed control means in accordance with the content of the temperature or the ambient temperature and the compressing speed set in the parameter and compressing speed setting means. It is to be noted that the temperature of the coolant contained in the concentrated grinding sludge may be that before the grinding sludge is supplied into the press unit or that after the grinding sludge has been supplied into the press unit.
By way of example, at the time of start-up of the grinding sludge compacting machine, the compacting operation is initiated with the compressing speed automatically determined according to the measured temperature and the measured ambient temperature. As the compacting operation proceeds, the coolant temperature and the ambient temperature increase with the machine warmed up and, accordingly, in pursuit for change in coolant temperature and in ambient temperature, the compressing speed is automatically, for example, stepwise increased to enable the compressing operation to take place under an ordinary state. In this way, the satisfactory compression of the grinding sludge can be achieved with the compressing speed determined properly in dependence on the change in coolant temperature and others.
Alternatively, the predetermined parameter may be the content of the coolant in the concentrated sludge, in which case the parameter measuring means measures the content of the coolant and, based on a result of measurement performed by the parameter measuring means, the compressing speed by the press unit is controlled by the compressing speed control means in accordance with the content of the coolant contents and the compressing speed set in the parameter and compressing speed setting means. It is to be noted that the coolant may be an oil-based coolant or a water-based coolant.
The content of the coolant contained in the concentrated sludge to be supplied into the press unit inevitably varies depending on a condition prior to the treatment. Once the coolant content varies, the compression of the grinding sludge will be affected as follows. If the coolant content is high, the grinding scraps and the coolant are mixed to form a sludge easy to flow out when it is forcibly compressed by the press unit and, accordingly, either is the yield of the grinding scraps that can be compressed reduced, or in the worst case it may occur the total amount of the grinding sludge will flow out to such an extent as to render the compression of the grinding sludge difficult. In such case, the squeezing operation has to be performed with the compressing speed lowered. On the other hand, if the coolant content is low, the coolant will not flow out in the form of a sludge and compression can easily be performed and, accordingly, the compressing speed can be accelerated.
In view of the foregoing, by measuring the coolant content at all times and performing a control of the compressing speed in dependence on the change in coolant content based on the result of measurement, it is possible to achieve the compression efficiently with any fault in compression eliminated and with no need to lower the compressing speed.
The parameter measuring means may not be always limited to measure the coolant content directly, but may be designed to measure the coolant content in consequence. Accordingly, the parameter measuring means may be of a type capable of measuring an advanced position of a pressure applying piston, provided in the press unit, during a compressing operation. In this case, the parameter and compressing speed setting means has set therein a threshold value representative of a position, which corresponds to an ordinary advanced end of the advanced position of the piston, and a compressing speed for each division divided by such threshold value, and the compressing speed control means preferably compares a result of measurement of the piston advanced position, measured by the parameter measuring means during a compressing operation, with the threshold value, to thereby control the compressing speed in accordance with the content set in the parameter and compressing speed setting means.
The advanced position of the pressure applying piston of the press unit during the compressing operation varies depending on the coolant content in the concentrated grinding sludge. Specifically, if the coolant content is high, the advanced position will be forwardly of the position assumed when the coolant content is ordinary. Accordingly, by automatically cyclically measuring the advanced position of the piston, the compressing speed is lowered when the advanced position is forwardly of a threshold value that is set as the position assumed when the coolant content is ordinary. By so doing, even where the compression of the concentrated grinding sludge is difficult to achieve because of the high coolant content, a satisfactory compression can be achieved.
The parameter measuring means may be of a design capable of measuring the coolant content in terms of change in compressing pressure. By way of example, the parameter measuring means may measure a length of time required for a predetermined compressing pressure to be attained subsequent to start of compression when the concentrated sludge is compressed by the press unit. In this case, the parameter and compressing speed setting means has set therein a threshold value of the length of time and a compressing speed for each division divided by the threshold value, and the compressing speed control means compares the length of time, measured by the parameter measuring means, with the threshold value to thereby control the compressing speed in accordance with a content set in the parameter and compressing speed setting means.
Where the grinding sludge is to be compressed to provide the briquette, the coolant is squeezed during the first half of the compressing process and the grinding scraps are compressed during the latter half of the compressing process. For this reason, during the first half of the compressing process, a relatively low compressing pressure effective to squeeze the coolant is sufficient. For this reason, when the low compressing pressure is employed during the first half of the compressing process, the speed of movement of the pressure applying piston is affected by the concentrated sludge supplied into the squeezing chamber and, hence, the length of time required for the predetermined compressing pressure to be attained varies. If the coolant content is high, the coolant quickly fills up the squeezing chamber and quickly attains a predetermined compressing pressure at which switching of a low compressing pressure over to a high compressing pressure takes place. By monitoring the length of time required for the threshold value, that is the predetermined compressing pressure at the low compressing pressure, to be attained subsequent to such a phenomenon and then by controlling the compressing speed at the high compressing pressure according to the length of time so required, a stabilized normal compression of the grinding sludge can be realized.
In a second aspect, the present invention provides a grinding sludge compacting machine for compressing for making a briquette of a grinding sludge by inserting a concentrated grinding sludge formed by filtering a grinding sludge, produced in a grinding line by grinding hardened component parts while containing a coolant, into a press unit comprising a cylindrical mold fixed on a machine bench, a first piston reciprocatingly movably inserted in the cylindrical mold and a second piston arranged in face-to-face relation with the first piston, and compressing the concentrated sludge. In this compacting machine, the second piston has one end of a diameter larger than an inner diameter of the cylindrical mold.
With this compacting machine, the concentrated sludge supplied into the cylindrical mold is compressed by and between the first and second piston to provide the briquette. The second piston has one end that is of a diameter larger than the inner diameter of the cylindrical mold and is used to close the annular open end of the cylindrical mold when brought adjacent thereto and, therefore, upon completion of the compressing operation, the second piston is retracted in a direction away from the cylindrical mold while the first piston pushes the compressed material, that is, the briquette to eject the latter out of the cylindrical mold. In this way, since the second piston when retracted away from the cylindrical mold opens the annular open end of the cylindrical mold, no relative slippage such as observed in the gate type compacting machine will occur in the surface of the second piston and also in a surface of the compressed material that contacts such surface of the second piston and, consequently frictional wear hardly occur in the surface of the compressed material contacting the surface of the second piston. Sealing required to avoid blow-off of the grinding sludge during the compressing operation is achieved at and between the annular end face of the cylindrical mold and the second piston. Also, since the sealing is achieved at and between the annular end face of the cylindrical mold and the second piston, unlike the plug-like double cylinder type, even when the inner peripheral surface of the cylindrical mold undergoes frictional wear as the resultant briquette is compressed or pushed by the first piston, the sealing function will not be adversely affected. The grinding sludge compacting machine according to this aspect is thus substantially free from any influence which would otherwise be brought about by the frictional wear and can therefore work (perform the compressing operation) for a prolonged period of time in a stabilized manner, resulting in reduction in maintenance cost.
Preferably, the end of the second piston defines a gap in cooperation with an annular end of the cylindrical mold when the second piston is held in position adjacent the cylindrical mold, said gap defining a coolant drain passage. The gap referred to above may be of a size within the range of 0.05 to 1.0 mm.
The capability of the coolant being drained will considerably affect the efficiency of the compressing operation and the quality, but if the gap between the end of the second piston and the annular end face of the cylindrical mold is utilized as the coolant drain passage, a drain circuit for drainage of the coolant can easily be defined. If this gap defining the coolant drain passage is too small, the drainage of the coolant will be adversely affected, but if this gap is conversely too large, a problem would occur that the grinding sludge will blow off from the cylindrical mold or that the grinding sludge will be clogged within the gap to such an extent as to result in incapability of the coolant being drained. Accordingly, when the gap is chosen to be of a size within the range of 0.05 to 1.0 mm, a favorable drainage of the coolant can be secured and, on the other hand, it is also possible to avoid any possible blow-off of the grinding sludge.